“Just War” theory can be seen as an effort of the church to understand the situation of why war never ceases throughout the world and ages, and to determine the ethical teaching about war. This article will show that the Orthodox Christian faith`s views regarding “Just War” has been developed on the Just-War theory of John Chrysostom. In 2003 the Ecumenical Patriarch of Constantinople Bartholomew I identified two views on war (including any kind of violence). One is that war is justifiable as an armed defense against oppression and violence; the other that war is never permissible because war and violence are never means used by God in order to achieve a good result. We see the coherence of the modern Orthodox position on war through Chrysostom in the fourth century and then Constantine-Cyril in the ninth century. In his treatise, On the Priesthood, Chrysostom suggests an ethical distinction between the actions of the clergy and the actions of the laity. The hierarchy between the priest and laity is the foundation of Chrysostom`s faith and deeds. Since the priests are responsible for the doctrinal and spiritual state of the church, they are required to give uncompromising obedience to Christ`s teaching. However, the ethics for the laity are not that strict. His drawing of a sharp line between the priests and laity was extended to the just-war theory. For Chrysostom, priest or monks are prohibited to participate in any form of violence no matter what. But for the laity, it is forgivable in certain situations. An explanation of the yes and no sides of just-war theory is found in Constantine-Cyril, who understands Jesus` commandments within a hierarchal matrix. For him, John 15:13 is the pinnacle of all other commandments. While Jesus` mandate requiring nonviolence in Matt 5:38-44 is very important to follow, John 15:13 is telling about the greatest love the Christians can ever practice. In this verse, a Christian`s participation in war against injustice is justifiable. One step beyond that, Cyril states that safeguarding one`s neighbors and sacred persons is a duty for Christian soldiers. And those soldiers` death on the battle field is as praiseworthy as a martyr`s. Constantine-Cyril`s view on war is legacy of Chrysostom in the ninth century. In conclusion, the position of the Orthodox Church about war has two aspects. Chrysostom`s two aspects of yes and no in participating in war and violence laid the foundation of the medieval and modern Orthodox position of Just- War.